The invention relates to a vehicle body structure that constitutes a part of the body of a vehicle or the like.
A side member constituting a part of the body of a vehicle or the like is comprised of, for example, a floor side member 1 that extends along the longitudinal side of a floor portion of the vehicle and a front side member 2 that is positioned in front of the floor side member 1 as shown in FIG. 5. The front side member 2 is comprised of a kick up portion 3 that rises up from the front end of the floor side member 1, a front side member body 4 that extends forward from the kick up portion 3, and so forth. The front side member 2 in FIG. 5 is substantially straight in the longitudinal direction if viewed from above, and the front side member 2 has a high energy absorbing efficiency in inhibiting the deformation of the vehicle body in offset impact.
In the above-mentioned front side member 2, a flat area 5 that is relatively wide in the vertical direction is formed at the side including a boundary between the kick up portion 3 and the front side member body 4. In the case of a vehicle crash, the impact resistance of the kick up portion 3 must be increased to improve the energy absorbing efficiency of the front side member body 4. As there is the need for inhibiting the deformation of the flat area 5, the kick up portion 3 is provided with partition-shaped bulkheads 6, 7 functioning as reinforcing materials in order to increase the impact resistance of the kick up portion 3. If, however, the bulkheads 6, 7 are provided in order to inhibit the deformation of the kick up portion 3, the weight of the front side member 2 is increased.
In view of the above, it would therefore be desirable to provide a vehicle body structure that is capable of improving the impact resistance of a kick up portion without using any bulkheads to thus reduce the weight of a front side member.
According to the present invention, a front side member has a front side member body that is shaped like a cylinder having a substantially octagonal sectional form extending from the front end to the rear end is disposed at the side of an engine room in a vehicle, thereby improving energy absorbing efficiency. A pair of an inner member and an outer member constituting the front side member body and a kick up portion are joined together at a joint where a portion at the rear end of said front side member body and a portion at the front end of said kick up portion are concaved to be in contact with each other and are joined together, and thus a first closed section is formed at an upper side of the joint and a second closed section is formed at a lower side of the joint. This improves the impact resistance of the kick up portion. Moreover, the respective ridge lines of the front side member body having the octagonal sectional form are continuously formed from the front end to the rear end of the front side member body, and this further improves the energy absorbing efficiency. Further, the portions between the kick up portion and the front side member body are joined together to form the upper first closed section and the lower second closed section. This improves the impact resistance of the kick up portion without using any bulkheads to achieve the satisfactory energy absorbing efficiency of the front side member body and reduce the weight of the front side member body.